This invention relates to inter-network communications, and more particularly relates to fault-tolerant communications between networks.
The SONET standard provides for inter-working between ring networks. The SONET ring inter-working has two versions: (1) drop and continue and (2) dual transmit. SONET ring inter-working was not designed with mesh networks in mind, and therefore cannot be employed “as-is” to mesh networks. SONET ring inter-working must be substantially modified in order to provide resilience to mesh-to-mesh or mesh-to-ring or ring-to-mesh communications.
Ring-based networks in general do not consist of just one ring, but contain multiple rings. Mesh networks, on the other hand, typically are addressed as one large mesh, even though the mesh in fact comprises multiple meshes. If the mesh is perceived as one large mesh, then there is no need for mesh inter-working. Contrary to this conventional wisdom about mesh networks, the applicants have discovered that mesh inter-working is an important aspect of mesh networks. Mesh inter-working is needed for at least three reasons:
(1) Networks owned by different companies need to communicate with each other, while remaining separate entities, to avoid visibility into each other's internal workings and to avoid faults in one network from affecting another network.
(2) Sub-networks resulting from the break up of one large network to facilitate management also need to communicate with each other.
(3) As network managers migrate from ring networks to mesh networks, there will be a need to inter-work the resulting mesh networks.
None of the foregoing problems is subject to an obvious solution. The present invention addresses these problems and provides a solution.